Tapir, Circe, Snakecase

I have a code below

import io.circe.generic.auto._
import io.circe.Encoder
import io.circe.generic.extras._, io.circe.syntax._

implicit val config: Configuration = Configuration.default.withSnakeCaseMemberNames

case class User(firstName: String, lastName: String)

print(User("Foo", "McBar").asJson)

Its supposed to output something like

  "first_name" : "Foo",
  "last_name" : "McBar"

But I get

  "firstName" : "Foo",
  "lastName" : "McBar"

what Am I doing wrong? i thought giving implicit config will be enough !!!


  • import io.circe.generic.auto._ does not use Configuration.

    If you want to use configration you have to use io.circe.generic.extras.auto._.

    Generic extras (io.circe.generic.extras) is not an extension to standard derivation (io.circe.generic) but an alternative, and they don't mix well in the same file if you use auto.